Electric cable



Jan. 3, 1933. M. 'BARBERIS ET AL ELECTRIC CABLE Filed March 2, 1931 of electric tramways and railways;

\ ing for Patented Jan. `3, 1933 l UNITED STATES "PATENT oFFlcE' MARIO BARBERIS AND UGO BAGGI, or Timm,t ITALY, AssrG'Nozas, BY MEsNE ASSIGN- MENTS, TO S. I. R. T. I. (SOCIET ITALIANA RETI TELEFONICHE INTERURBANE), 0F

MILAN, ITALY, A JOINT-STOCK COMPANY OF ITALY ELECTRIC CABLE It is known that underground cables are subject to frequent disturbancesowing to the insufcient protection afforded by the armorings of the usual type.

The corrosion of the lead covering or sheath which is the cause of the above mentioned disturbances is .due chieiiy:

(1) To the effect of electrolysis generated by the stra or transient currents, such as e. g. the dispersion currents of return cables (2) To the chemical action of stances dissolved in thel ground.

The result is that when the cable is laid in proximity to conductors traversed by electric current or in a ground containing acid substances, the lead covering or sheath is attacked after a more or less short time and as the corrosion extends in depth and width moisture is allowed to enter thencable which is inevitably grounded. n

This invention relates to a protective coatelectric underground cables which preserves them against'the injurious action of transient currents and ofthe acid sub-` stances contained in the ground.

According to this invention two or a plurality of layers of bitumenor of a neutral bituminous material are applied on the lead covering.

The `single figure is a vertical transverse cross section through the cable, showing a'n ordinary electric cable therein.

Referring to the drawing, the numeral 1 designates the lead covering of a conventional form of cable 1a. A bitumen covering 2 is applied around the outer periphery of the lead covering in the following manner. First by laying a very thin layer of bitumen at 80 to 110 C'. and thereon a second layer v of bitumen at 70 to 80 C.. then a rubber i band or layer 3 is applied to the bitumen layer, and on this latter the varnislied tapes made of paper and numbered 4, 6, 8 and 10, alternating with bitumen layers 5. 7, 9 and 11. A layer of bituminated jute is applied on the bitumen layer ll and covered with an armoring 13 formed by two iron bands. Fi-

nally an outer layer of bituminated jute 14? is laid on the armoring.

the sub-n 519,570,.and in Italy November' 21, 1930.

The rst layer which is very thin is applied at a temperature between 80 and 110 C. and it firmly adheres to the tube; its high temperature improves the adhesion of the second layer which is successively applied at 70 to 80 C. The second layer which is of harder bitumen is thicker than the former and once it hasI set it forms on the cable a continuous tube.

A ribbon of rubber of suitable composition is wound spirally with largely overlapping edges on the second bitumen layer and is y protected against moisture by one or a plurality of paper tape layers made water-tight by impregnating them with suitable insulating varnishes such as wax and paraiiine. The paper tapes are preferably wound in the same direction as the rubber band as this improves the adhesion. Layers of a suitable bituminous mixture are alternated with the paper tapes and are applied at a temperature such as will partly melt the varnish impregnating the paper tapes thus improving the cohesion of the coating which acquires the appearance and properties of a continuous tube structure. The usual armoring is laid on this coating and protects the cable chiey against mechanical stresses.

The band protecting the cable against transient currents is conveniently made according to this invention of non-vulcanized rubber containing sulphur.

What we claim is:

1. In an electric cable in combination with a lead sheath protecting the cable, a layer of neutral bituminous material surrounding the lead sheath, an insulating rubber band wound about said layer, a water-tight paper tape wound on the insulating band and a bitumen layer on the paper tape. p A,

2. In an electric cable, in combination with a lead sheath protecting the cable, athin layer of neutral bituminous material applied on the lead sheath at a relatively high temperature, a second thicker layer of harder bituminous material applied on the former layer at a less high temperature, an insulating. rubber band wound about said layer, a watertight paper tape wound on the insulating band and a bitumen layer on the paper tape.

3. In an electric cable, in combination with a lead sheath protecting y the cable, a thin layer of neutral bituminous material applied on the lead sheath at a relatively high temperature, a second thicker layer of hardervbitiminous material applied on the former layer at a lower temperature, a band of non vulcanizedrubber containing sulphur wound on the second layer of bituminous material, atape of water-tight paper impregnated witli wax and paraine varnish wound in the same direction as the rubber band and a. layer of bitumen on the paper tape.

4. In an electr1c cable, in combination with a lead sheath `,protecting the cable, a thin layer of neutral bituminous material applied on the sheath at a temperature of about 95 C., a second thicker layer of harder bituminous material applied on the first layer at a f temperature of about 75 C., anl insulating rubber band wound about said layer, a watertight paper tape Wound on the insulating band and a' bitumen layer on the paper tape. 5. In an electric cable, in combination with a lead sheath protecting the cable, a thin layer l of neutral bituminous material applied. on

the sheath at a temperature of about 95 C., a second thicker layer of harder bituminous material applied on the first layer at a temperature of about 75 C., a band of non vulcanized rubber `containing sulphur wound y on the second layer of bituminous material,

a tape of water-tight paper impregnated with wax and paraine varnish wound in the same direction as the rubber band and a layer of bitumen on the paper tape.

In testimony that we claim the foregoing as our invention, we have signed our names.

` MARIO BARBERIS. UGO BAGGI. "Q 

